1. Field of the Invention
The present invention relates to a picture display device. More particularly, the present invention relates to a picture display device such as a device for displaying picture element data on a liquid crystal display using a cycle steal display system.
2. Description of the Prior Art
In the prior art, display devices for displaying picture element data on the upper and lower display areas as two divided areas of the screen region of a liquid crystal display are shown for example in Japanese Patent Laying-Open Nos. 28671/1980, 78598/1982 and 132791/1983. Any of these devices displays a television picture and the like on a liquid crystal display. In these picture display devices, the display region is divided into upper and lower two areas for the purpose of decreasing the burden of time sharing operation dependent on the responsivity of the liquid crystal display.
However, as the number of picture elements on the liquid crystal display increases, not only the responsivity of the liquid crystal display itself but also the responsivity of the peripheral circuit including a drive device become worse conspicuously. For example, if a television video signal fed as serial data at a predetermined speed is directly applied to the drive device, the picture quality becomes coarse and the picture displayed is liable to sway, which would lead to bit degradation due to impossibility of follow-up. Therefore, various methods are used, for example, a method in which a video signal applied by means of a frame memory is temporarily stored and the writing speed and the reading speed of the frame memory are changed, or a method in which frame memories for two frames are used alternately for writing and reading, or a method in which a video signal is regularly selected and fed to the drive device, is adopted for the purpose of eliminating the above stated drawback. However, these methods are not preferred because a large-capacity memory is required or the picture elements displayed are coarse and the picture quality is deteriorated.